Gonadotropin-releasing hormone and conception of Holsteins.

Effects of gonadotropin-releasing hormone (100 micrograms) and time of artificial insemination on fertility, were examined in lactating dairy cows at first, second, and third services. Inseminations were either soon after detected estrus (0 h) or 12 h later, and cows were given gonadotropin-releasing hormone or saline after inseminations. Conception at first service was not improved by hormone treatment. But conception rates at repeat services were improved by nearly 21% when cows were treated with gonadotropin-releasing hormone within 30 s after insemination. Inseminations soon after detection of estrus (0 h) followed by hormone treatment resulted in the highest conception rates for all services. Time of the insemination (0 versus 12 h) had no effect on conception. Administering gonadotropin-releasing hormone at repeat services should improve conception rate of lactating dairy cows.